1382 GEOLOGY OF OHIO. 
Coat Seam No. 1. 
This is probably Coal A of the Pennsylvania geologists, and is popularly 
_ known in \north-western Pennsylvania, where it is largely mined, as 
the Sharon, or Ormsby coal. It is there sometimes covered with heavy 
patches of Conglomerate, and has been regarded as a sub-Conglomerate 
coal, but, as I have shown elsewhere, its true position is above the Con- 
glomerate. In Ohio it is the lowest seam in the series, usually from 
twenty to fifty feet above the Conglomerate. It is best known here as the 
“Briar Hill,” “Mahoning Valley,” or “Massillon” coal. In Jackson county 
it,is largely mined, and in the southern part of the State is known as the 
‘Jackson coal.” This has heretofore been regarded as the most valuable 
coal seam in the State, from the fact that in many localities it is of good 
thickness, of remarkable purity, and well adapted in the raw state to 
the smelting of iron ores. It is, indeed, a typical furnace coal, and forms 
the fuel by which fully one-half the iron produced in the State is manu- 
factured. Proof of its purity is furnished by the fact that a large amount 
of iron is made with it which is used for the manufacture of Bessemer 
steel, car wheels, etc. Unfortunately, this is an exceedingly irregular 
seam. This peculiarity is due to two causes, which have been already 
referred to, viz., it was the first accumulation of carbonaceous matter in 
the great peat bog that subsequently became our coal basin. As a con- 
sequence it occupies only the lower portions of the irregular bottom of 
this basin, and was never deposited over the ridges and hummocks which 
fringed the margin, or, as islands, dotted the surface of the old coal marsh. 
The second cause of its absence is that it was extensively cut away by 
currents of water in rapid motion which swept over the coal marsh in a 
submergence that followed its formation. The channels excavated by 
these currents were generally filled with sand, and this now converted 
into sandstone forms the horsebacks which cut out the coal. They are 
connected with the great stratum of sandstone which I have called the 
Massillon sandstone, and which is generally separated from the coal by 
a bed of shale ten to forty feet in thickness. Coal No. 1 has its best 
development in the Mahoning Valley. It is here very compact, working 
in large blocks, from which fact it has received the name of Block coal, 
and is remarkably pure, as is shown by borings made in the analyses 
given below. 
In Geauga county the Briar Hill coal reaches as far south as Burton, 
but only in a narrow strip and detached islands, and is then of little 
value. 
In Portage county it is mined at Palmyra, but its line of outcrop is here 
concealed by heavy beds of Drift, and what its development is has not yet 
been determined. It has been struck in borings made in the valleys of 
